Elimination reactions and configurations of 1-methylcyclohexyl derivatives, including steroid analogues

Abstract

Analysis of elimination products does not necessarily establish the configurations of 1-methylcyclohexyl derivatives. Dehydration of 3β-methyl-5α-cholestan-3α- and 3β-ol [(I) and (III)] with phosphoryl chloride–pyridine gives, as reported earlier, the endocyclic (II) and the exocyclic olefin (IV), respectively, as major products. Dehydration with thionyl chloride–pyridine, however, did not conform to this pattern: the results of dehydrohalogenation of the 3α-halogeno-3β-methyl derivatives (V) also appeared to be anomalous. Similar reactions of 1-methyl-4-t-butyl-cyclohexyl derivatives, and of 12-methylspirostan-12-yl compounds, indicate that the proportions of olefinic products may be decided as much by the ‘leaving group,’ and by the base employed, as by the conformational features of the compound examined.